The present invention relates to an endless band conveyor of the flexible type having a band portion which is caused to follow a helicoidal path of transport consisting of a plurality of band windings stacked one upon the other, wherein the helicoidal band portion is supported, at the outer edge thereof, by a fixed helicoidal support bar and, at the inner edge thereof, by each band winding being supported by an underlying winding through an extra conveyor comprising an endless line of stacking blocks, said blocks keeping successive band windings at a distance from each other defined by the height of the blocks so as to provide spacings between the stacked band windings, and said blocks being adapted to transfer driving forces from an inner drum to the inner edge of the band, and whereby said line of stacking blocks, at the respective lower and upper ends of the helicoidal band portion, is guided by guiding means into support of or from support of, respectively, the inner edge of the helicoidal band portion.
In a band conveyor of the type disclosed in EP 0293095, the conveyor band is, at the inner edge thereof, supported and frictionally advanced in the helicoidal path by the stacking blocks of an extra conveyor, the blocks having a height defining the desired spacing between two successive windings in the stack of helicoidal band windings.
The band conveyor thus known, has the drawback that the conveyor band thereof is subjected to wear and tear at its inner edge due to the frictional contact with the stacking blocks which, in turn, are subjected to wear and tear by the inner edge of the band, and consequently the conveyor band which represents large costs, has to be replaced just because the inner edge has been worn out, whereas the remaining part of the band may be as good as new.
It is the object of the invention to remove this drawback while simultaneously concentrating the most essential wear and tear at component parts which are relatively easy to exchange and are less costly than the conveyor band.
In accordance with the invention this is achieved in that the driving drum has circumferential and frictional engagement with the stacking blocks which are acting as liners between the drum and the band, in that those of the stacking blocks being in contact with the drum, are in slip-free or backlash-free mechanical engagement with the radially innermost edge of the band, and in that the frictional engagement of the drum with the stacking blocks of the extra conveyor allows the blocks to be displaced not only along the surface of the drum axially thereof, but also along the surface of the drum circumferentially thereof.
Hereby is achieved that the band conveyorxe2x80x94in addition to being economically constructible by use of standard conveyor bands without particularly designed edge areasxe2x80x94is able to avoid the heavy wear and tear on the inner edge of the conveyor band and to have the wear and tear limited substantially to the extra conveyor alone, so that it is sufficient to replace the worn out stacking blocks without having to replace the flexible band at the same time.
Moreover, the band conveyor of this invention may expediently include firmly anchored slide bars in the surface of the driving drum, said slide bars providing the frictional engagement of the drum with the stacking blocks during said frictional engagement of the extra conveyor with drum.
By means of friction between the slide bars of the drum and the stacking blocks of the extra conveyor, driving forces are transferred from the rotating drum to the stack of band windings. Hereby the band is affected by driving forces along the entire length in the stack of band windings, and the wear and tear on the drum due to the frictional engagement with the extra conveyor is limited to the replaceable slide bars.
Furthermore, the band conveyor of the invention may advantageously have stacking blocks which include coupling means adapted to be brought into and out of locking engagement with the inner edge of the band before and after the formation of the helicoidal stack of windings.
In a preferred embodiment the band is hereby prevented from being displaced relative to the extra conveyor, and mutual wear and tear is thereby prevented. Moreover, the band is prevented from moving away from the drum and out of the stacking blocks of the extra conveyor, for instance during standstill without longitudinal pulling forces in the band.